Wireless carriers, such as Verizon™, Sprint™, Cricket Wireless™, and so forth, provide a variety of wireless telephony and data communication services around the world via wireless networks. Such services include wireless voice, data, text messaging, and so forth. A multitude of wireless networks, large and small, create a web of overlapping, sometimes inconsistent network accessibility. Depending on a user's geographic location, multiple wireless communication networks may be within communication range of the user's wireless device, yet each wireless network may potentially offer different types of services at varying levels of quality, and at different cost structures.
Large regional and national wireless carriers help simplify the complexity to end-users by offering subscription plans which allow a paying service subscriber to access the wireless carriers “home” network as well as “roaming” networks operated by other wireless carriers who have a business relationship with the home network wireless carrier.
Through these business relationships, a wireless carrier can greatly expand the geographic coverage area accessible to paying subscribers without having to extend the home network itself. The paying subscriber benefits from such inter-carrier business relationships through extended geographic coverage, and further benefits from convenient access to multiple networks through a single subscription plan.
The wireless carriers develop a complex list of preferences for various geographic zones based on the cost structure or other parameters stipulated by the contractual business relationships. For example, a wireless carrier will prefer to use its own home network infrastructure at a lower cost, rather than a contractually available roaming network, typically at a higher cost, regardless of quality.
In geographic areas where a home network is not accessible, a wireless carrier may have preferred contractual terms with a particular roaming network, but no agreement or unsatisfactory terms with another. In other situations, the wireless carrier may choose not to contract with any roaming network provider, despite the availability of such a network.
Each wireless carrier embodies these preferences in a “Preferred Roaming List” or “PRL” which is used to control a cellular telephone's selection or non-selection of available cellular networks in any given geographic area. The PRL lists by geographic region, networks accessible from that geographic region, and an order of preference for those networks. A cellular phone operating in a particular geographic area receives a System Identification Number (SID) from each network within communication range and selects the network identified by the wireless carrier as the most preferable.
Because the preferences are based on contractual relationships and preferences which are determined by the wireless carrier, a service subscriber may be denied service entirely, despite the availability of a cellular network, or the service subscriber may be connected with a network that does not offer desired services or provides unacceptable wireless signal quality in a particular geographic area, despite the availability of a cellular network that offers the desired services or provides superior wireless signal quality in that particular geographic area.
These problems are exacerbated for Machine-to-Machine (M2M) implementations which rely upon the cellular networks to transmit telemetry data, receive remote instructions, trigger automated alarms, or request emergency assistance. For example, consider a residential security system, installed in a fixed location, that is unable to notify authorities of an alarm condition because the cellular network deemed as “preferred” by the wireless carrier is not available or has inadequate signal quality and an available cellular network is deemed “less-preferred,” despite being within communication range of the security system and capable of transmitting the requisite data.